Joint contractures that occur after head injury, stroke, spinal cord injury and cerebral palsy (CP) have devastating functional consequences. Contractures represent a vexing obstacle to the rehabilitation process and many times the only treatment for contracture is surgical tendon transfer or release, both of which are highly invasive and do not necessarily restore muscle function. The purpose of this proposal is to understand the changes that occur in muscles after contracture formation and to test conservative treatment options. The specific upper motor neuron lesion (UMN) population to be studied is children with cerebral palsy (CP). This is due to the large number of children with CP seen in the rehabilitation setting and the number who undergo surgical correction for contracture (making their muscle tissue available). Biomechanical and structural properties of muscle from patients with contractures will be measured in vitro after surgery to determine the basis for the changes in passive mechanical properties. Then, a complete gene expression profile will be generated on these tissues to determine how the physiological pathways activated explain the functional results obtained. The specific aims of this proposal are: (1) to define the biological and biomechanical properties of muscles from children with CP and to contrast and compare these properties with age- and muscle-matched normal tissue, age- and muscle- matched atrophic tissue, (2) To determine the extent to which muscle and/or connective tissue properties are accurately reflected by the clinical exam, and (3) To measure the biological response of human semitendinosus muscles compared to age- and muscle-matched normal tissue, and age- and muscle-matched atrophied tissue. This proposal is based on preliminary obtained from actual human muscles after contracture due to upper motor neuron lesion. In addition to increasing our understanding of muscle after contracture, these experiments may lead to novel, nonsurgical interventions to treat skeletal muscle contractures.